This invention pertains to refractory brick and particularly such brick with built-in allowance for their thernal expansion when heated in service.
It is well-known that refractory brick expand when heated in service, and it is well-known to allow for this thermal expansion. When the refractory brick have metal plates on one or more of their faces, it is known to provide thermal expansion allowance by dimples, waves, or other collapsible configurations of the metal plate. Particularly, it is known to provide a greater amount of expansion allowance at the hot face of the brick by this means, for example as shown in U.S. Pat. Nos. 2,192,642 and 3,139,048.
However, not all refractory brick are used with metal plates, and when such plates are absent, other means have been used to provide for thermal expansion, for example by means of cardboard or asbestos strips. Again, it is known to provide greater expansion allowance at the hot face than at the cold face, for example as shown in U.S. Pat. No. 3,324,810.
However, the attachment of metal plates or cardboard or asbestos strips complicates the manufacturing process and makes it more expensive. Accordingly, the industry has been seeking for a simpler method of providing automatic thermal expansion allowance in refractory brick, particularly brick which are required to be free of metal casing, as is true in certain applications.
It has been suggested in U.S. Pat. No. 1,191,271 that thermal expansion allowance be provided in refractory brick by putting an increased taper on the brick adjacent the hot face. When such brick are put in place during construction of the furnace, there results a gap between the brick at their hot face ends, this gap being filled by expansion of the brick when the furnace or other structure is heated.
However, in constructing a furnace or kiln of the brick of U.S. Pat. No. 1,191,271 it is necessary to be very careful in laying them up, particularly in an arcuate construction such as a furnace roof or rotary kiln, that the brick are not tipped so that there is no gap at the hot face end of the brick, but a gap at the cold face end. Obviously, this erroneous method of installation destroys the presence of any thermal expansion space, and most probably will lead to broken or spalled brick when the furnace structure is heated. Because of this shortcoming of the brick of U.S. Pat. No. 1,191,271, they have found little use in practice.
The present invention is directed to the overcoming of this problem.